The following relates to the sensor arts, chemical sensing arts, biological organism sensing arts, and related arts.
Biological and chemical sensors find application in diverse areas, such as environmental monitoring, safety monitoring, potable water processing, and so forth. Highly sensitive sensor devices have been fabricated using on functionalized surfaces that interact with an analyte or organism of interest.
A chemical sensor employing functionalized nano-width regions as sensor elements is disclosed in Yang et al., U.S. Pat. No. 7,009,268. In this sensor, the resistances of a Wheatstone bridge are nano-width doped semiconductor regions (e.g., silicon, germanium, diamond, SiC, SiGe alloy, GaAs or another III-V semiconductor, GaN, or so forth) that are doped n-type or p-type. Metallic layers or lines are disposed at each of the four “corners” of the Wheatstone bridge to interconnect the nanowires. The nanowires include a sensing coating or other adaptation to produce a response to a stimulus such as a chemical or biological agent.
Meyers et al., U.S. Pub. No. 2004/0121509 A1 also discloses a nanowire-based Wheatstone bridge configured as a chemical sensor device. In this design, the four legs of the Wheatstone bridge include respective nanowires, one of which has a functionalized surface to act as a chemical sensor.
Such sensor devices can provide very high sensitivity, possibly even sufficient to detect a single analyte molecule, or a single biological cell of interest. However, the devices generate low power signals requiring substantial amplification, and can suffer from nonlinear response. Sensor devices employing power amplification may be unsuitable for use as wireless devices; however, wireless chemical sensors are advantageous in some applications in which the ambient is caustic or toxic, or the sensor device is intended to operate under high pressure, or in an otherwise challenging environment. The use of a high-precision bridge circuit such as a Wheatstone bridge can reduce or eliminate the need for amplification; however, the bridge circuit must be tuned with high precision (for example, by precisely matching resistances in a Wheatstone bridge) in order to realize the theoretically achievable high sensitivity.